Forensics experts will no longer need to collect fingerprints from smooth surfaces, according to Australian research, which has tested new chemical sprays that allow prints to be lifted from surfaces as rough as bricks.

The researchers also presented their findings this week at a Sydney conference, Lifting the Identification Profile, which celebrated the 100th anniversary of the introduction of fingerprinting in Australia.

Fingerprints are one of the most important ways police identify criminals. But picking them up relies on ways of making them visible. Traditionally, this means using a fine powder, such as aluminium or titanium dioxide, which sticks to the fingerprint's moisture and oily components.

Powdering is cheap, quick and easy to use. But 10% of prints are obliterated when the powder is brushed on. And forensic experts cannot always use the method to pick up old prints that have lost their 'stickiness'.

The biggest limitation of powdering, however, is it needs to be used on smooth and non-porous surfaces. Rough surfaces like bricks have generally been out of bounds for fingerprint collectors.

Scientists have proposed sprays containing iodine-benzoflavone or ruthenium tetroxide as a way of getting prints from difficult surfaces. The sprays are easier to apply to rough surfaces and can treat large areas quicker.

But until this study, researchers had not publicly tested how the sprays picked up prints from different surfaces.

Flynn and colleagues tested the effectiveness of powdering and sprays, giving Australian police their first comprehensive guide to what works best on various surfaces.

They found that there was no universal technique for use on all surfaces.

"The fingerprint powders in standard use are still effective on most surfaces, but the chemical sprays have expanded the armoury, giving better results on some difficult surfaces," said Professor Claude Roux, who supervised the work as part of Flynn's PhD.

"On glass and treated wood we found that powdering was still the superior technique, whereas the spray techniques produced better results on wallpaper, vinyl and brick."

As part of the research, the team needed to adjustment the spray formulations, like replacing CFC-containing solvents and developing a cheaper form of ruthenium tetroxide. Roux described their results on picking up fingerprints on bricks as "outstanding".

"The real promise of the sprays is the quality of results on very rough surfaces, with the possibility that even rocks at outdoor crime scenes will yield valuable fingerprint evidence."

But the researchers said using sprays provided a higher health and safety risk at the crime scene than conventional powders. This means money would need to be spent on personal protective equipment and cleaning up the crime scene.